Can't get ember engines running

I've created a standalone routable engine with ember-engines 0.4.0, ember-cli 2.10.0.

I get this error if I call the engines index route (/things/):

Assertion Failed: Asset manifest does not list any available bundles.

Consuming App router.js:

this.mount('things', { as: 'things' });

Engine App routes.js:

this.route('index', { path: '/' });

The engine is 'installed' via a symlink in the node_modules/ dir of the consuming ember-cli app. (See here why).

Just for fun I've tried to change the routes to test if that works ...

Consuming App router.js:

this.mount('things', { as: 'things' });

Engine App routes.js:

this.route('index', { path: 'new' });

I've called /things/new and got an UnrecognizedURLError.

Also if I place a console.log('...'); in the engines index.js, I can't see any output. Seems like it isn't loaded at all.

The setup was inspired by the official README and the official example repos.

Any idea how to fix this Ember Engines setup?